JP2003526955A - Flexible frequency / time division duplex in wireless communication systems - Google Patents

Abstract

  (57) [Summary] The flexible channel scheme supports full-duplex radio frequency communication between a base station, eg, a PWT base station or a DECT base station, and a group of mobile terminals. Downlink communication from the base station to the terminal is performed via a first radio frequency carrier, and uplink communication from the terminal to the base station is performed via a second radio frequency carrier. Each carrier is configured to provide a time division multiple access data stream of N time slots, where N is an integer, such that the two carriers together provide a 2N time slot system. Within each frame, data from the base station to the terminal is transmitted on a first carrier during a first time slot, and data from the terminal to the base station is transmitted on a second carrier during a second time slot. However, the first and second time slots are offset by a time offset that can vary over the communication link. The disclosed system provides a unified architecture that allows a single time division multiple access hardware platform to efficiently and selectively support either time division duplex or frequency division duplex.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to wireless communication systems, and more particularly to time division multiple access (TDMA).
) Regarding the duplex method in the system.

[0002]

[Prior art]

Most of the time division multiple access wireless communication systems are time division duplex (TDD, ti
me-division duplex system or frequency division duplex (FDD,
Any of the frequency-division duplex) schemes is adopted to separate the uplink transmission and the downlink transmission. Both duplex schemes have some advantages and disadvantages, so both schemes are routinely utilized in wireless communication applications.

For example, the Personal Wireless Telecommunications (PWT) standard uses time division multiple access with time division duplex for frequency planning and signal packet and time slot allocation. Such time division multiple access / time division duplex schemes are very convenient for many business wireless communication applications (eg, small campus systems with micro or pico cells).

[0004]

[Problems to be Solved by the Invention]

On the other hand, time division multiple access with either time division duplex or frequency division duplex is a licensed personal communication service (PCS) according to customer requirements and market requirements.
It can be favorable for a frequency band. In other words, the structure of personal communication service systems is largely determined by the service providers who have acquired a portion of the frequency spectrum, so the technology and frequency utilization implemented in such systems ultimately results in Requirements and legal and practical constraints. After a first customer requests a time division multiple access / time division duplex system for a particular business wireless application, a second customer can time division multiple access / frequency division for a wireless local loop application. May require system.

Therefore, service providers often need to switch between duplexes. However, switching between schemes is usually a double effort and thus wastes considerable time and resources. For example, it is generally not possible to use a common hardware platform for both systems, because traditional time division duplexing and frequency division duplexing are fundamentally different. As a result, two development teams are usually assigned and two separate manufacturing lines are usually established to provide for both time division duplex and frequency division duplex implementations.

[0006] Therefore, there is a need for a flexible duplexing scheme that allows a communication system to be adapted to meet the diverse needs of customers without requiring modification of the underlying system hardware architecture. There is.

[0007]

[Means for Solving the Problems]

The present invention fulfills these and other needs by providing a flexible split duplex mechanism in a time division multiple access communication system. More specifically, the disclosed system is a mixed or hybrid split duplex where uplink and downlink transmissions are separated in frequency but the time slots associated with transmission and reception are also separated in time. Use the mechanism. Hybrid duplex is referred to herein as frequency / time division duplex (FTDD, frequency-ti).
Me division duplex), which allows alternative split duplex schemes to be selectively implemented within the communication system without requiring modification of the underlying system hardware architecture.

The frequency and time division duplex system of the present invention offers the advantages of lower power consumption and reduced hardware complexity typically associated with conventional time division multiple access / time division duplex systems. However, the interference characteristic is also improved by separating the frequency bands of the uplink and the downlink. Furthermore, the proposed system allows a single hardware platform to be used for multiple technologies and applications. For example, a base station designed for a business wireless system based on time division multiple access / time division duplex technology can be modified with a slight change to a wireless local loop based on conventional time division multiple access / frequency division duplex technology ( WLL) applications can also be used. Thus, embodiments of the present invention significantly reduce the one-time technical costs typically associated with technology and product development. As a result, the development plan and manufacturing cycle of the implemented system can be shortened, and the service provider and product provider can respond to customer and market demands more quickly.

In an exemplary embodiment, the base station is configured to transmit a downlink communication signal to the mobile station on a first carrier frequency and receive an uplink communication signal from the mobile station on a second carrier frequency. A transceiver includes a downlink communication signal and an uplink communication signal transmitted and received over successive time division multiple access frames, each frame including a plurality of time slots. For each active communication link between the station and a particular mobile station, a first time slot in each frame is assigned for downlink communication to that particular mobile station, from the particular mobile station. A second time slot in each frame is assigned for uplink communication, and the assigned first and second time slots are separated in time by a fixed time offset. Advantageously, the duration of the fixed time offset can be different (eg for each call established) on each active communication link. For example, if each frame has a duration T, contains 2N time slots, and each time slot has a duration T / 2N, the fixed time offset of each active communication link is m from 1 to 2N. ΔT = (T / 2N) × m can be set as an integer in the range of −1.

In an alternative embodiment, the base station is configured to transmit a downlink communication signal to the mobile station on a first carrier frequency and receive an uplink communication signal from the mobile station on a second carrier frequency. A transceiver includes a downlink communication signal and an uplink communication signal transmitted and received over successive time division multiple access frames, each frame including a plurality of time slots. Advantageously, the transceiver's downlink signal processing path and uplink signal processing path share common signal processing components. For example, shared signal processing components can include one or more filters, local oscillators, and modems.

The above and additional features of the present invention are described in more detail below with reference to the illustrative examples shown in the accompanying drawings. Those skilled in the art should understand that the described embodiments are provided for purposes of illustration and understanding, and that all equivalent embodiments are contemplated herein.

[0012]

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a wireless communication system 100 in which the teachings of the present invention may be implemented. As shown, this exemplary wireless system includes ten cells or coverage areas C1 ...
C10 includes 10 base stations B1 to B10, a timing master TM, and 10 mobile stations M1 to M10. Such wireless systems can be constructed, for example, according to the Personal Wireless Telecommunications (PWT) standard, and are therefore used to provide mobile communications, for example indoors or throughout a premises including many buildings and outdoors. can do. Generally, a wireless system has 10 cells, 10 base stations,
And much more than 10 mobile stations, but for purposes of illustration,
Ten for each is sufficient.

As shown, there may be one or more base stations located in each cell. Although the base stations are shown in FIG. 1 as being located towards the center of the cell, each base station could instead be located anywhere within the cell. Base stations located towards the center of the cell typically use omnidirectional antennas, while base stations located towards the cell border typically use directional antennas. The timing master TM or wireless switch maintains timing synchronization between base stations as is well known in the art. The timing master can be connected to the base station by cable, wireless link, or both.

Each base station and each mobile station includes a transceiver for transmitting and receiving communication signals over the air interface. Base stations and mobile stations typically communicate using forms of time division multiple access, frequency division multiple access, or code division multiple access (ie, TDMA, FDMA, CDMA) as is known in the art. As the mobile station moves within and between cells, communication with at least one base station is always possible.
As a result, mobile station users can make, receive, and answer calls anywhere within the entire coverage area of the system.

In order to clarify the features and advantages of the hybrid frequency division / time division duplex (FTDD) scheme according to the present invention, the conventional time division duplex (TDD) scheme and frequency division duplex (FDD) scheme are described as follows. This will be described below with reference to FIGS. 2A, 2B, 3A and 3B. Without loss of generality, we use the channel definitions in the personal wireless telecommunications standard to exemplify conventional time division multiple access (TDMA) / TDD systems.
The channel definitions may differ between standards, but the underlying concepts of multiplexing and duplexing are the same.

FIG. 2A shows uplink communication and downlink communication according to the conventional TDD method. As illustrated, the signal transmitted from the TDD base station B20 to the TDD handset M20 and the signal transmitted from the TDD handset M20 to the TDD base station B20 are temporally separated. As shown in FIG. 2B, a predetermined time interval T is a single TDMA / TDD.
When representing the duration of frame T20, the separation between uplink and downlink transmissions is typically one half of a given time interval T, or T / 2. In a personal wireless telecommunications system, each frame has a duration of 10 milliseconds,
It includes 24 data slots (carrier timeslots). Twelve time slots are used for transmission (from TDD base station B20 to TDD handsets M20) and the remaining twelve time slots are received in one data frame. (I.e., for transmission from TDD handset M20 to TDD base station B20). Transmission and reception are separated by some fixed (or fluctuating) time, but they share a common frequency band. Thus, the channels of such a system are defined by a given frequency and time reference pair.

Such a TDMA / TDD system is widely used in various wireless communication applications. An advantage of these systems is the frequency efficiency advantage of using a carrier of a common frequency for both uplink and downlink transmissions. Moreover, since the transmit and receive are separated in time, a single hardware path (including filters, local oscillators, etc.) can be used for both functions. As a result, TDD systems are relatively low cost. Also, because the receiving hardware can be turned off during transmission (and the transmitting hardware can be turned off during reception), the TDD system consumes relatively little power.

In contrast, frequency division duplex (FDD) systems require separate frequency bands for uplink and downlink communications. This is due to the fact that the transmit and receive operations are performed simultaneously at different frequencies. Therefore, the channels in an FDD system are defined by the frequency of operation. FIG. 3A shows downlink communication between a conventional FDD base station B30 and a conventional FDD handset M30, and FIG.
An exemplary TDMA / FDD frame T30 is shown in FIG. Since both transmission and reception are accomplished simultaneously, separate hardware paths are required for both base station and terminal. As a result, FDD systems are typically more costly and consume more power than conventional TDD systems. However, FDD systems provide relatively low inter-channel interference and may be preferable from an inter-system perspective.
In other words, the FDD scheme may be needed for a system to be compatible with an approximate system that uses parts adjacent to its frequency spectrum. As a result, FDD systems are also widely adopted in wireless communication applications.

While both TDD and FDD systems offer certain advantages, neither is ideally suited for all wireless communication applications. Furthermore, as mentioned above, due to the fundamental difference between TDD and FDD, it is difficult to limit the configuration of either system to meet the needs of a particular application. Advantageously, the present invention provides a hybrid frequency time division duplex (FTDD) scheme, which offers certain advantages over both conventional types of systems, and further, a single hardware The configuration allows virtual instant adaptation to any wireless communication application.

To illustrate the FTDD system of the present invention, two TDMA data frames are used.
Includes N time slots (N is an integer), N slots are reserved for downlink transmission from the base station to the portable (mobile station) and the remaining N slots are from the portable to the base station. Defined as reserved for uplink transmission. Without loss of generality, assuming the time durations of the uplink and downlink slots are u and d, respectively, the duration T of a single frame is given by:

N (d + u) = T (1) Since the transmit and receive time slots usually have the same time duration (ie d = u), half a frame or T / 2 is usually reserved for downlink transmission. And the other half of the frame is reserved for normal uplink transmission.

According to the invention, a dual link is established with both frequency and time separation. Specifically, the uplink frequency f _u is separated from the downlink frequency f _d by a predetermined frequency offset Δf as in the following equation.

[0023]   f_u= F_d-Δf (2) Or   f_u= F_d+ Δf (3)   Equations (2) and (3) describe the frequency division duplex aspect of the system.
. In addition to frequency separation, time separation is also provided. Specifically, base station and portable
Uplink and downlink communications to and from
Even separated. The specific time offset is T / 2N seconds / slot cycle.
2N slots of the frame length. Time duplexing is then usually
S for link packets_u(T_l), S for downlink packets _d (T_l± ΔT), in which case t_lUplink Pake
Can be defined as the start time of the   ΔT = time offset = (T / 2N) × m (1 ≦ m ≦ 2N−1) (4)
(M is an integer, and according to the present invention, each of the
May vary depending on the communication link). Therefore, time division and frequency division
Aspects of the combined system are generally S for uplink packets. _u (T_l, F_u), S for downlink packets_d(T_l+ ΔT, f_u ± ΔF) or S_d(T_l-ΔT, f_uIt can be described as ± ΔF).

Thus, according to the invention, the uplink and downlink transmissions are on separate frequencies and in pairs of allocated time slots, one pair of time slots being a base station and a mobile station. Assigned to each active link established between and. For each active link, the assigned uplink
A time slot is a time offset ΔT within each TDMA frame,
It precedes or follows the corresponding assigned downlink time slot. The assigned time slot pair is then maintained for the duration of the link.

The selection of uplink and downlink time slots for each link can be based, for example, on a channel selection process that determines the best link configuration. The determination of the best link configuration may be based on, for example, an assessment of adjacent channel and / or co-channel interference present at call setup. Advantageously, either the base station or the mobile station can be responsible for time slot selection and allocation. For example, the base station can select the uplink time slot based on the interference condition of the base station, and the mobile station can select the downlink time slot based on the condition of the mobile station. Alternatively, the base station may select both uplink and downlink time slots independently or when instructed by the mobile station.

It is noted that a single base station can be used to support portable over a particular coverage area because each base station is not limited to a particular portion of a frame for uplink or downlink transmissions. I want to. In other words,
Each slot in each TDMA frame can be assigned to either an uplink or downlink transmission, and the time offset between the assigned uplink and downlink time slot pairs is equal to each active
Since each link can be different, a single base station can communicate with a mobile station using any available time slot configuration that would be preferable to the mobile station. Of course, a single base station can support most N dual links simultaneously (2N time frames per TDMA frame).
Assuming traffic conditions (assuming slots), a second base station can be added to the coverage area to provide full time and spectrum efficiency (ie, both base stations have 2N base stations). Can support both simultaneous calls).

FIG. 4A shows an FTDD base station B communicating according to the above-mentioned TDMA / FTDD system.
40 and FTDD terminal M40. As shown, uplink and downlink communications are separated in both frequency and time. FIG. 4B then illustrates an exemplary combination of time slot pairs within a single base station TDMA / FTDD data frame T40a. Those skilled in the art should understand that the pair combination of FIG. 4B is merely an example, and all possible pairs are contemplated by the present invention. Furthermore, FIG.
Those skilled in the art will appreciate that although each uplink and downlink pair of B utilizes the same time offset (ie, ΔT = T / 2), each pair may utilize different time offsets as described above. I want you to understand. However, for purposes of illustration, assuming that the illustrated time slot pair has effect for the first base station, it is shown in FIG. 4C, for example, co-located without causing interference to the first base station. 2 shows a pair of complementary time slots that can be used by a second base station. First
And the second base station both provide full time and spectrum efficiency for the coverage area in which they are located (ie, each frequency in each time slot in each TDMA frame is an uplink communication. And used for either downlink communication).

In accordance with the present invention, appropriate base station synchronization is used to enable the handset to communicate with any base station in the overall system. As is well known in the art, such base station synchronization can be performed via the timing master TM as shown in FIG. In embodiments in which the time offset ΔT between the paired uplink and downlink time slots varies over the communication link (ie, each active communication link may use different time offsets), handover. In order to implement a), a suitable overhead signaling is required between the base stations (ie during handover, information identifying the currently assigned pair is passed between the base stations). But,
In an embodiment where each active link utilizes a common time offset ΔT,
Overhead can be significantly reduced. For example, the co-pending "Fixed Request" filed on the same date as this specification, which is hereby incorporated by reference in its entirety.
ncy-Time Division Duplex in Radio Co
See U.S. Patent Application No. _ entitled "Mmmunications Systems". Those skilled in the art will appreciate that the aforementioned synchronization can be accomplished by simple software modification of existing systems.

The exemplary embodiment of the TDMA / FTDD system described above uses the band definition of the US Personal Communications Service with the PWT (E) time division definition for the uplink and downlink frequencies. This embodiment uses a fixed ΔT = T / 2 for all duplex links and operates with the following parameters.

ΔT = T / 2 = 5 msec ΔF = 80 MHz T / 2N = 416.667 μsec S _u (t _l , f _u ) S _d (t _l ± 5 msec, f _u +80 MHz) As described above. In addition, the TDMA / FTDD scheme of the present invention provides, among other advantages, the power saving benefits typically associated with conventional TDMA / TDD systems. For example, according to the disclosed FTDD scheme, uplink transmission and downlink transmission are temporally separated, so that the transmission path and the reception path of the transceiver of the base station or mobile station can share certain components. . FIG. 5 illustrates this aspect of the invention.

In FIG. 5, the exemplary base station transceiver 500 comprises a transmit signal processing path and a receive signal processing path. As shown, the transmit signal path comprises first and second transmit blocks 510, 520, first and second transmit / receive blocks 530, 540, a local oscillator 550, a duplexer 560, and an antenna 570. Further, the reception signal processing path includes a local oscillator 550, a duplexer switch 560, an antenna 570, and first and second reception blocks 580 and 590.

The first transmission block 510 can include, for example, a conventional up-converter, and the second transmission block 520 can include, for example, a power amplifier and a mixer. Further, the first reception block 580 includes, for example, a low noise amplifier (LNA).
) And a mixer, and the second receive block 590 can include, for example, a conventional down converter and limiter. The first send / receive block 530 may include, for example, a modem, and the second send / receive block 5
40 may include, for example, a bandpass filter. The transmission / reception switch 560 is
For example, it can be a two-way filter or a switch.

During downlink transmission, duplexer 560 couples antenna 570 to second transmit block 520 and isolates antenna 570 from first receive block 580. The baseband transmit signal is processed by the first transmit / receive block 530 and then blocks 510, 540, 520 before being transmitted via antenna 570.
Are up-converted, filtered, and amplified. Conversely, during uplink reception, duplexer 560 couples antenna 570 to first receive block 580 and isolates antenna 570 from second transmit block 520.
The radio frequency signal is received at antenna 570 and then amplified, filtered, and downconverted at blocks 580, 540, and 590, respectively, before being processed by first transmit / receive block 530. Certain components of the send and receive processing paths (ie, first and second send / receive blocks 53
The base station transceivers constructed in accordance with the present invention can be made smaller and less costly than conventional TDMA / FDD transceivers because they share common (and very expensive components in 0, 540). it can.

In summary, the present invention teaches a time division multiple access system that includes a flexible frequency division / time division dual mechanism. The disclosed system enables existing time division multiple access / time division duplex hardware to be utilized for applications where dual duplex frequency bands are required. The system maintains the flexibility of using either the same frequency band or separate bands for uplink and downlink communications. In each case, time-division duplex performance is maintained, minimizing hardware cost and power consumption.

Those skilled in the art should appreciate that the present invention is not limited to the specific exemplary embodiments described herein for purposes of illustration. Therefore, the technical scope of the present invention is defined not by the above description but by the claims appended hereto, and all equivalents that match the meaning of the claims are to be included therein.

[Brief description of drawings]

[Figure 1]   FIG. 1 illustrates an exemplary wireless communication system in which the teachings of the present invention can be implemented.

FIG. 2A is a diagram illustrating a base station and a mobile station that communicate according to a conventional time division multiple access / time division duplex method.

FIG. 2B is a diagram showing an exemplary time slot configuration in a conventional time division multiple access / time division duplex system.

FIG. 3A is a diagram illustrating a base station and a mobile station that communicate according to a conventional time division multiple access / frequency division duplex method.

FIG. 3B is a diagram showing an exemplary time slot configuration in a conventional time division multiple access / frequency division duplex system.

FIG. 4A is a diagram illustrating a base station and a mobile station that communicate by a flexible time division multiple access / frequency / time division duplex method according to the present invention.

FIG. 4B illustrates an exemplary time slot configuration in a flexible time division multiple access / frequency / time division duplex system according to the present invention.

FIG. 4C is a diagram showing an alternative time slot configuration in a flexible time division multiple access / frequency / time division duplex system according to the present invention.

[Figure 5]   FIG. 3 is a block diagram of an exemplary transceiver constructed in accordance with the present invention.

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE), OA (BF, BJ , CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, GM, K E, LS, MW, SD, SZ, UG, ZW), EA (AM , AZ, BY, KG, KZ, MD, RU, TJ, TM) , AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, D K, EE, ES, FI, GB, GD, GE, GH, GM , HR, HU, ID, IL, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, L U, LV, MD, MG, MK, MN, MW, MX, NO , NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, U G, UZ, VN, YU, ZW (72) Inventor Renzo, Michael             United States North Carolina             27502, Apex, Widget             Lane 314 (72) Inventor Shen, Kun             United States North Carolina             27502, Carry, Connor's Sir             Clou 110 F term (reference) 5K067 AA13 CC04 EE02 EE10 EE22                       EE72 GG03 JJ18 KK00

Claims (23)

[Claims] 1. A base station used in a wireless communication system including a plurality of mobile stations, wherein a downlink communication signal is transmitted to the mobile station at a first carrier frequency, and a downlink communication signal from the mobile station is transmitted at a second carrier frequency. A transceiver configured to receive an uplink communication signal, wherein the downlink communication signal and the uplink communication signal are transmitted and received via consecutive time division multiple access frames each including a plurality of time slots, For each active communication link between the base station and a particular mobile station, a first time slot in each frame is assigned for downlink communication to the particular mobile station and a second time in each frame is assigned. A slot is assigned for uplink communication from the particular mobile station and the assigned first and second time slots are fixed tie Base station, wherein the fixed time offsets may be different in duration on each active communication link. 2. The base station according to claim 1, wherein each time slot in the time division multiple access frame can be assigned to any one of downlink communication and uplink communication. 3. The base station according to claim 1, wherein the base station is configured to select a time slot assigned to uplink communication for each active communication link. 4. The base station according to claim 1, wherein the base station is configured to select a time slot assigned to uplink communication and downlink communication for each active communication link. 5. The time slot allocated for uplink communication and downlink communication is selected for each active communication link when instructed by the mobile station. 1. The base station according to 1. 6. Each frame has a duration T, includes 2N time slots, each time slot has a duration T / 2N, and the fixed time offset of each active communication link comprises: The base station according to claim 1, wherein when m is an integer in the range of 1 to 2N-1, it is given by ΔT = (T / 2N) × m. 7. A plurality of mobile stations and at least configured to transmit a downlink communication signal to the mobile station on a first carrier frequency and receive an uplink communication signal from the mobile station on a second carrier frequency. A wireless communication system including one base station, wherein the downlink communication signal and the uplink communication signal are transmitted and received via continuous time division multiple access frames each including a plurality of time slots, For each active communication link between the base station and the particular mobile station, the time slot of the first frame is allocated for downlink communication from the particular base station to the particular mobile station, and the time slot of the second frame is allocated. Time slots are assigned for uplink communication from the particular mobile station to the particular base station, and the assigned first and second tie Slot is separated in time by a fixed time offset, a communication system in which the fixed duration time offset, characterized in that to obtain different for each active communications link. 8. The communication system according to claim 7, wherein each time slot in the time division multiple access frame can be assigned to either one of downlink communication and uplink communication. 9. The base station is configured to select a time slot assigned to downlink communication and uplink communication for each active communication link with a mobile station. The communication system according to. 10. The communication system according to claim 7, wherein the mobile station is configured to select a time slot assigned to downlink communication and uplink communication. 11. The mobile station is configured to select a time slot assigned to downlink communication and the base station is configured to select a time slot assigned to uplink communication. The communication system according to claim 7, wherein: 12. Each time division multiple access frame has a duration T and includes 2N time slots, each time slot having a duration T / 2N, between a base station and a mobile station. Said fixed time offset of each active communication link of
The communication system according to claim 7, wherein is given by ΔT = (T / 2N) × m when is an integer in the range of 1 to 2N−1. 13. The communication system of claim 7, wherein the two base stations are co-located to provide full time and spectrum coverage for a particular system coverage area. 14. A communication method for performing communication between a base station and a mobile station in a wireless communication system, wherein the base station uses continuous time division multiple access frames each including a plurality of time slots. And a step of transmitting a downlink communication signal and an uplink communication signal between the mobile station, the downlink communication signal is transmitted from the base station to the mobile station using a first carrier frequency, The uplink communication signal is transmitted from the mobile station to the base station using a second carrier frequency, and further, for each active communication link between the base station and a specific mobile station, the specific mobile Assigning a first time slot in each frame for downlink communication to a station, and assigning a first time slot in each frame for uplink communication from the particular mobile station. Assigning a 2 time slot, the allocated first communication method characterized by comprising the steps of selecting a fixed duration time offset between the second time slot, the. 15. The method further comprising co-locating the base station with a similarly constructed second base station, thereby providing full time and spectrum coverage to the mobile station. The communication method according to claim 14, which is characterized in that 16. A base station for use in a wireless communication system including a plurality of mobile stations, wherein a downlink communication signal is transmitted to the mobile station at a first carrier frequency and the mobile station is at a second carrier frequency. A transceiver configured to receive an uplink communication signal from the downlink communication signal, the downlink communication signal and the uplink communication signal are transmitted and received via consecutive time division multiple access frames each including a plurality of time slots, A base station wherein the downlink signal processing path and the uplink signal processing path of the transceiver share a common signal processing component. 17. The base station of claim 16, wherein the shared signal processing component comprises at least one of a filter, a local oscillator, a modem. 18. For each active communication link between the base station and a particular mobile station, a first time slot in each frame is assigned for downlink communication to the particular mobile station, A second time slot in the frame is assigned for uplink communication from the particular mobile station, and the assigned first,
The base station according to claim 16, wherein the second time slots are separated in time by a fixed time offset. 19. Each time slot in the time division multiple access frame,
The base station according to claim 18, wherein the base station can be assigned to any one of downlink communication and uplink communication. 20. The base station of claim 18, wherein the duration of the fixed time offset can be different on each active communication link. 21. Each frame has a duration T, includes 2N time slots, each time slot has a duration T / 2N, and the duration of the fixed time offset of each active communication link. 21. The communication system according to claim 20, wherein is given by ΔT = (T / 2N) × m, where m is an integer in the range of 1 to 2N−1. 22. The base station of claim 18, wherein the fixed time offsets are of equal duration for each active communication link. 23. Each frame has a duration T, comprises 2N time slots, each time slot has a duration T / 2N, and the duration of said fixed time offset of each active communication link. 23. The base station according to claim 22, wherein is T / 2.